The present invention is in the field of laser gyros for measuring rotation, rotation rate, and rotation acceleration. Glass and single crystal fiber growth or manufacture has progressed remarkably during the last few years. Ring laser gyros utilizing glass or single crystal waveguide fibers are capable of solving some of the problems of conventional laser gyros. One of the problems which has proven very difficult to solve from the practical standpoint is the lock-in problem. The laser gyro operates on the principle that electromagnetic radiation propagates without regard to the motion of the media in which it is propagating. Radiation in a finite length path, therefore, takes longer to reach the far end of the path if the path is moving in the same direction as the radiation and conversely, the time is shortened if the path is moving in the opposite direction. The frequency of oscillation of a laser depends on the length of its closed path. If the path length increases slightly the frequency decreases and if the path length decreases slightly the frequency increases. In the special case of the ring laser the path length is closed by connecting the two ends of the laser instead of the practice in a standard laser where the path is closed by reflectors. The ring allows the radiation to propagate in both directions in an independent manner if the path is perfect. The problem is that a perfect path has been very difficult to construct and there is a tendency for radiation going in opposite directions to lock-in together. It is virtually impossible for the molecules in a gas laser not to cause some scattering of the radiation and consequent lock-in. Reflectors and path discontinuities can also cause radiation scattering and lock-in. These problems exist for both gaseous and solid lasers, but are avoided in a solid ring laser with a perfect crystal structure, as the instant invention. There have been several projects to develop single crystal fibers. Most of these projects were initiated to develop fiber reinforcing for such items as jet engine turbine blades. These projects were based on the knowledge that single crystal fibers are among the strongest of known materials. One of the more successful projects was carried out by Arthur D. Little, Inc., based on pulling crystals from a laser created melt-point on solid crystal material. This technique has allowed the pulling of zone-refined single crystal fibers of considerable lengths. Fibers of less than 50 microns diameter with less than 5 microns variations are typical. Work is in progress to pull such fibers to 5 microns diameter and many meters long. By cladding these fibers with a dielectric layer with a slightly lower index of refraction they become single mode waveguides. Single mode waveguiding follows the relationship: ##EQU1## in which:
a = the radius of a single crystal fiber,
.lambda. = the wavelength of the radiation in air,
n.sub.1 = the index of refraction of the fiber,
n.sub.2 = the index of refraction of the cladding.
Utilizing a Nd:YAG laser crystal (1.06 micron = .lambda.) with an index of refraction n.sub.1 of 1.83 and a cladding, n.sub.2, of 1.83 minus 0.1%, the fiber diameter should be less than 5 microns. Single crystals of this type are becoming available. Glass waveguide technology has progressed considerably more than has single crystal waveguide technology. Losses below 2db per kilometer and length to 10 kilometer have been reported. The instant invention is particularly directed to single crystal waveguide because it is anticipated that they will eventually be superior for fiber waveguide ring lasers. Theoretically, the losses and scattering in a single crystal fiber waveguide can be lower than glass, which will help solve the lock-in problem. Also, some single crystals such as Nd:YAG are effective Faraday rotators in axial magnetic fields. Variation of such a magnetic field changes the effective lengths of the opposite directions of propagation of energy in a ring laser, even with zero rotation of the laser. The field may be adjusted manually or automatically to provide a fixed off-set, so that F.sub.1 = F.sub.2 = some constant frequency, with or without rotation. This technique is a possible solution to the problem of lock-in.